1. Field of the Invention
This invention relates to a boom type mine drilling machine for drilling holes and installing roof bolts in a mine roof, and more particularly to an operator's compartment protected by an overhead canopy where the operator's compartment is movable upwardly and downwardly along a predetermined straight-line path and supports a drill steel guide for maintaining a drill steel along said path.
2. Background of the Invention
In underground mining, it is the present practice to support the roof of a mine with roof bolts and, in certain instances, with horizontal timbers or metallic tie members secured to the surface of the roof by a plurality of roof bolts that extend through predrilled holes in the timbers or tie members. Also, it is known to substitute the metallic tie members and timbers with a rectangular roof plate that is supported in bearing relation with the roof surface when the roof bolt is fully engaged in the bore hole. A boom supported roof drill as illustrated in U.S. Pat. Nos. 3,319,727 and 3,375,880 includes boom members that support the drill pot for movement of the drill steel in a straight line as it is advanced into the rock strata. The boom is positioned on a self-propelled vehicle that is movable to preselected locations in the mine entry for installing roof bolts in accordance with a preselected pattern that provides the optimum support of the overhead roof.
The mobile boom-type drilling machines include a linkage mechanism for moving the drill pot mounted on the front end portion of the drill boom in a vertical linear path. Means is also provided for mechanically varying the linkage to permit the drill to move in a path at an angle and in a vertical plane. In this manner, fore and aft angular adjustment for the drill steel is made and it is possible to change the angular path of the drill from a straight line vertical path to a vertical fore or aft angular path relative to the mining machine.
It is the conventional practice to stabilize the machine during roof drilling and bolting operations particularly for machines mounted on rubber tires. This is accomplished by stabilizing jacks which are lowered to engage the mine floor and transfer the weight of the machine from the wheels to the jacks. Because the front end of the machine is raised when the jacks are lowered into engagement with the ground, the boom linkage is adjusted to support the drill pot in a fore position at a preselected angle from the vertical to the ground. Thus, when the jacks are engaged the machine body is raised to move the drill pot aft and align the drill steel for upward movement along a vertical linear path.
When the bolt holes are being drilled in relatively hard materials substantial problems are encountered in aligning the drill steel with the axis of the bore hole during the drilling operation, especially where the bolt holes are a substantial depth. It has been found extremely difficult to maintain the drill steel aligned with the bore hole throughout the entire drilling operation. When one drills in hard material, frequently the drill steel will penetrate the hard material and be deflected slightly or tilt relative to the vertical axis. Continued vertical drilling when the drill steel is tilted or deflected and not aligned with the bore hole causes the drill steel to rub against the sidewall of the bore hole, especially at a location adjacent the roof surface. Under certain circumstances, the rubbing of the drill steel on the collar of the hole causes the drill steel through friction to overheat and break. As is well known, this frictional rubbing can also cause a fire hazard at the mine face in gaseous mines. The rubbing of the drill steel against the sides of the bore hole also absorbs a substantial amount of the thrust energy imparted to the drill and reduces the drilling efficiency.
To maintain axial alignment of the drill steel with the bore hole it is the conventional practice for the operator, particularly in "spotting" the drill head to start the bore hole, to steady the drill steel with his hand. The operator continues to hold the drill steel as it advances into the mine roof to maintain the drill steel in a vertical axis for drilling a bore hole in a straight line. Thus the operator uses his hand to align the drill steel with the axis of the bore hole when the drill steel deflects and rubs against the sidewall of the bore hole. Such a practice subjects the drill operator to substantial risk of injury and should be avoided.
Centralizers for guiding movement of a drill steel along a predetermined straight-line path during starting of the bore hole are known in the art such as illustrated in the following U.S. Pat. Nos.: 2,350,658, 2,350,659, 2,350,660, 2,350,661, 2,365,680, 2,365,681, 2,365,682, 2,365,683, 2,365,684, 2,365,685, 2,365,686, 2,365,687, 2,394,806.
These references relate generally to drill steel centralizers for a hammer type face drilling machine where a pair of cooperating centralizer arms are mounted on a guide and include guide portions for engaging the body of the drill steel. The arms center the drill steel during starting of the drill hole. Once the drill hole is started the guide portions are released from engagement with the drill steel.
U.S. Pat. No. 3,842,610 discloses a mine drilling machine having a boom supported drill chuck assembly with a split guide collar for holding upright a rock drill. The guide collar is supported by the drill chuck assembly and is movable into and out of surrounding relation with the rock drill positioned in the chuck. The guide collar moves upwardly with the assembly. U.S. patent application, Ser. No. 793,723, filed May 4, 1977, discloses a separate boom for a drill guide that maintains the drill steel in a vertical linear path as it drills the bore hole. The above application also includes a protective canopy mounted on the drill boom for providing the operator with overhead protection.
Operator protective devices, such as overhead canopies, are conventionally used with mine roof drilling and bolting machines. U.S. Pat. No. 3,893,520 discloses a canopy assembly for a dual boom drill. The dual boom drill of U.S. Pat. No. 3,768,574 features a canopy that is raised and lowered relative to a pair of drill booms. The canopy overlies a platform upon which an operator may be situated. The canopy and platform may be raised and lowered as a unit or independently of one another.
While it has been suggested by the prior art systems to provide drill steel guides for boom type mining machines, there is need for a boom type mining machine that includes a drill steel guide and means for supporting the drill operator on a movable platform which provides the operator with overhead protection.